Sexual Development in Phytophthora

本研究将以植物病原植物疫霉属为模式，阐明卵菌属真菌交配和有性孢子发育的发育生物学和遗传学。卵菌是一类重要但研究较少的低等真核生物，包括许多具有经济和环境意义的动植物病原体、其他病原体的生防剂和腐生植物。在卵菌中，就像在许多其他微生物中一样，交配是生命周期的重要组成部分。交配导致卵孢子的形成，卵孢子是一种耐用的结构，可以在季节之间存活下来，引发疾病流行。性周期还使基因在种群中流动，产生可能更适合的菌株，因为决定致病性、寄主偏好、杀菌剂抗性和其他特性的新基因组合。这项提案的大部分内容都集中在致病疫霉上，这是一种毁灭性的植物病原体(马铃薯晚疫病)，每年造成数十亿美元的损失。它也是研究卵菌生物学的一个很好的模型系统。致病疫霉是异交的，当不同交配类型的分离物通过激素相互作用时，通常会诱导卵孢子。在之前的工作中，鉴定出了9个在交配过程中诱导的基因。在这个项目中，将使用多学科方法来解决这种交配调节基因的功能和调节。这将需要识别更多的受调控基因，并对部分基因研究其结构、蛋白质产物的细胞定位以及沉默和强迫表达的影响。除了对致病疫霉的研究外，这些基因的表达还将在一种同源的种--菜豆疫霉中表现出来，该种在单一培养中产生卵孢子。还将对交配过程中分泌的新化学物质进行初步研究。这项调查的结果将产生概念上和实际上的影响。我们将更好地理解用于指导真核细胞分化、应对压力和形成生存结构的不同策略。发展中的重要问题将被解决，如细胞通信、自我/非我识别、细胞类型确定、基因调控和信号转导。同源和异源交配系统的基础也将被阐明。卵菌的交配调控可能不同于其他低等真核生物，如子囊菌和担子菌，后者缺乏与卵菌的分类亲和力。从长远来看，如果能够确定控制交配的因素，就有可能通过使用合理的基于机理的抑制剂而不是对环境有害的化学物质来控制病原菌的生活史，从而控制植物病害。

This research will elucidate the developmental biology and genetics of mating and sexual spore development in oomycete fungi, using the plant pathogenic genus Phytophthora as a model. Oomycetes are an important but understudied group of lower eukaryotes that include many economically and environmentally significant pathogens of plants and animals, biocontrol agents of other pathogens, and saprophytes. In oomycetes as in many other microbes, mating is an important element of the life cycle. Mating results in the formation of oospores, which are durable structures that can survive season-to-season to initiate disease epidemics. The sexual cycle also enables gene flow through populations, yielding strains that may be more fit due to new combinations of loci determining pathogenicity, host preference, fungicide resistance, and other traits. Much of this proposal focuses on P. infestans, which is a devastating plant pathogen (potato late blight) that causes many billions of dollars of damage per year. It is also a good model system for studying oomycete biology. P. infestans is heterothallic, and oospores are normally induced when isolates of different mating types interact through hormones. In previous work, nine genes induced during mating were identified. In this project a multidisciplinary approach will be used to address the function and regulation of such mating-regulated genes. This will entail identifying additional regulated genes, and for a subset of the genes studying their structure, cellular localization of their protein products, and the effects of silencing and forced expression. In addition to studies of P. infestans, the expression of the genes will also be characterized in a homothallic species, P. phaseoli, which produces oospores in single culture. Preliminary studies of novel chemicals secreted during mating will also be performed. Results from this investigation will have conceptual as well as practical impacts. A better understanding will be obtained of the diverse strategies used to direct eukaryotic cell differentiation, to respond to stress, and to form survival structures. Important issues in development will be addressed such as cellular communication, self/nonself recognition, cell type determination, gene regulation, and signal transduction. The basis of homothallic and heterothallic mating systems will also be illuminated. It is likely that mating in oomycetes is regulated differently than in other lower eukaryotes such as ascomycetes and basidiomycetes, which lack taxonomic affinity to oomycetes. In the long term, if the factors which control mating can be identified, it might be possible to control plant diseases by manipulating the life cycles of pathogens using rational mechanism-based inhibitors instead of environmentally harmful chemicals.